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PRACTICE / Electric dipole

A neutral pair can still require work to turn

A rigid electric dipole has charges ±2 nC separated by 4 mm in a uniform field of 1.0×10⁵ N/C. It is turned quasistatically from aligned to anti-aligned with the field.

What work must an external agent supply?

Organize the givens & assumptions
  • Charge magnitude = 2 nC
  • Separation = 4 mm
  • E = 1.0×10⁵ N/C
  • Angle: 0 → π

Rigid ideal dipole in a uniform electrostatic field; no translational displacement, friction or net kinetic-energy change. Dipole moment points from negative to positive charge.

  1. A8.0×10−7 J8.0\times10^{-7}\ \mathrm J
  2. B−1.6×10−6 J-1.6\times10^{-6}\ \mathrm J
  3. C1.6×10−6 J1.6\times10^{-6}\ \mathrm J
  4. D0 J0\ \mathrm J

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